Due to the increasing communication of control devices in many areas of technology, for example in the automotive field, efforts are being made to supplement or expand communication solutions with methods that are built on the technologies designated Ethernet and based on the IP (Internet Protocol) network stack. An example is the so-called SOME/IP (Scalable Service-Oriented Middleware over IP). This is based on the IP network stack and was developed for use in Ethernet networks in vehicles.
A service discovery method makes it possible to resolve the IP address and the port of a sought service in SOME/IP. After the address resolution has taken place, a connection can be created to the node having the corresponding service, and its service can be used. There can be various instances of a service that can be found using a single search request for the particular service. A service discovery method, for example that of SOME/IP, can in principle be initiated from two sides. A node that requires a particular service can initiate the search by sending a search request provided for this purpose (referred to as a FIND message hereinafter). The FIND message contains the description of the sought service (for example a service ID). A provider of this service can react with a response in which the sought service is offered (referred to as an OFFER message hereinafter). However, the initiative can also originate from the provider of a service, so that the provider sends out an OFFER message without a concrete request from a potential subscriber. In this way, a node that requires a particular service can be informed concerning the availability without itself having to send out a search request.
Standardly, the SOME/IP protocol is not designed for a routing over different subnetworks having different address regions. Because the addresses valid only in a subnetwork are contained in the protocol header, a gateway between two subnetworks has to adapt the address information. This is a problem that is also known from other network protocols. A proposal for the operation of a gateway so as to solve this problem is not contained in the SOME/IP specification. The use of SOME/IP for the bus systems CAN and FlexRay, widely used in vehicle systems, is seen as not practicable, and for this reason only particular Ethernet subnetworks are addressed in a vehicle.
Patent document DE 10 2010 042 601 A1 discusses a method for distributing information in hierarchically constructed networks. Here, nodes of one level communicate to the assigned node of the next-higher level which information they provide and which information they require. In this way, it is possible to realize a hierarchically constructed distribution of information. In this known method, the communication in a subnetwork always runs via the assigned node of the higher level. The method of DE 10 2010 042 601 A1 starts from the assumption that a node knows which information it requires. The node sends this information concerning an offered service without a previous request by a consumer or subscriber. This means that the requirement is known ahead of time, and a static configuration is thus present. As a consequence, a particular area node knows which information the nodes below it provide and require. In this way, it can ascertain the need for information that has to be requested from the next-higher level, because it is not available at the lower level. The presence of a plurality of instances capable of offering a particular service is however not provided in the known method.
Moreover, this method has disadvantages in a dynamic environment in which for example the individual nodes become active temporally independently of one another. This is because the information actually supplied and required by the lower-level nodes is not known until all nodes have communicated this. Thus, a static configuration is disadvantageous in particular given dynamically changing lower-level nodes.